1. Technical Field
The present invention relates generally to a system for sending a signal to a device and in particular, to a system for safely sending an electrical signal to a device. Still more particularly, the present invention provides an improved system for safely sending an electrical signal to a device by preventing the inadvertent sending of the electrical signal to the device.
2. Description of the Related Art
It is desirable to prevent the inadvertent jettison of weapons from military aircraft. Presently, circuits for preventing the inadvertent jettison of weapons employ additional electromechanical or solid state relays and test cables in the pylons; and, modification of the existing flight line testers is also required. The relays are added to the pylon to fulfill a single point failure requirement and the test cables and tester changes are required to detect the single point failure. The disadvantage of this system is the necessity for additional wiring, additional installed relays, and changes to standard test equipment.
One alternative method for preventing the inadvertent switching of power is illustrated in Fisher et al., U.S. Pat. No. 4,599,675. A switching system is utilized which comprises two transistors in series with a solenoid coil. A monitoring system is utilized to monitor the state of the two switches such that no single electrical fault can result in an inadvertent energization of a control valve. Specifically, in the event that one of the switches is off while the other is conducting, the monitoring system inhibits switching on the switch that is in the "off" state. Although such a system is useful in the event that one of the transistors fails, situations exist, such as current spikes, wherein the event that causes one transistor to fail will also Cause the other transistor to fail. In such a situation, the circuit has failed in a "on" state. Additionally, such systems typically pass current through the load (generally a solenoid coil) in order to test the state of the transistors. Allowing current to pass through a weapon or other pyrotechnic device is not a desirable situation.
Therefore, it would be desirable to have an improved switching system to prevent the inadvertent switching of power or a signal to a device and to reduce the potential for accidental release of weapons or firing of pyrotechnic devices,